1. Field of the Invention
The present invention relates to a magnetic head for perpendicular magnetic recording for use to write data on a recording medium by means of a perpendicular magnetic recording system.
2. Description of the Related Art
The recording systems of magnetic read/write apparatuses include a longitudinal magnetic recording system in which the magnetization of signals is directed along the plane of a recording medium (the longitudinal direction), and a perpendicular magnetic recording system in which the magnetization of signals is directed perpendicular to the plane of a recording medium. It is known that the perpendicular magnetic recording system is harder to be affected by thermal fluctuation of the recording medium and capable of providing higher linear recording density, compared with the longitudinal magnetic recording system.
Magnetic heads for perpendicular magnetic recording typically have, like those for longitudinal magnetic recording, a structure in which a read head unit having a magnetoresistive element (hereinafter, also referred to as MR element) for reading and a write head unit having an induction-type electromagnetic transducer for writing are stacked on a substrate. The write head unit includes a coil, a main pole and a return path section. The main pole has an end face located in a medium facing surface facing a recording medium. The coil produces a magnetic field corresponding to data to be written on the recording medium. The main pole passes a magnetic flux corresponding to the magnetic field produced by the coil, and produces a write magnetic field from its end face. The return path section is connected to the main pole. The return path section passes the magnetic flux corresponding to the magnetic field produced by the coil.
A magnetic head for use in a magnetic disk drive such as a hard disk drive is typically provided in a slider. The slider has the medium facing surface. The medium facing surface has an air inflow end (a leading end) and an air outflow end (a trailing end). An airflow that comes from the air inflow end into the space between the medium facing surface and the recording medium causes the slider to slightly fly over the surface of the recording medium.
Here, the side of the positions closer to the leading end relative to a reference position will be referred to as the leading side, and the side of the positions closer to the trailing end relative to the reference position will be referred to as the trailing side. The leading side is the rear side in the direction of travel of the recording medium relative to the slider. The trailing side is the front side in the direction of travel of the recording medium relative to the slider.
Magnetic heads for perpendicular magnetic recording are increasing in frequency of write signals to achieve higher recording densities. For such magnetic heads, it is thus required that the write current flowing through the coil should exhibit a rapid rise. To meet the requirement, it is particularly effective to shorten a magnetic path that passes through the return path section, which is provided on the trailing side of the main pole, and through the main pole. This is because an end of a record bit to be recorded on a recording medium is determined by the position of the trailing-side end of the end face of the main pole located in the medium facing surface. The return path section and the main pole define a space for the winding of the coil to pass through. To shorten the magnetic path passing through the return path section and the main pole, it is effective to reduce the number of turns of the coil.
U.S. Pat. No. 8,867,168 B2 discloses a first magnetic head and a second magnetic head. The first magnetic head includes a coil extending approximately ¾ time around the entire perimeter of the main pole as viewed from the medium facing surface. The second magnetic head includes a coil extending approximately 7/4 time around the entire perimeter of the main pole as viewed from the medium facing surface.
For the first magnetic head, however, the coil is unable to provide a sufficiently large magnetomotive force. For the second magnetic head, the winding of the coil passes twice through the space defined by the main pole and the return path section located on the trailing side of the main pole. Thus, it is not possible for the second magnetic head to sufficiently shorten the magnetic path passing through the return path section and the main pole.